Loud speaker cone suspension



Nov. 27, f934,' c, ME -K 1,982,443

LOUD- SPEAKER CONE SUSPENSION I Filed June 3, 1929 /7M I 23 5; I3

'namic motor or minates in a ring portion edge 25 at the base of thecone '7 is as thin,

Patented Nov. 27, 1934 I UNITED STATES PATENT OFFICE Application June 3,1929, Serial No. 367,988 12 Claims. (01. 181-31) The object of thisinvention is to provide an improved form of damping for large sizedirect acting sound radiators. A more specific object is to provide suchdamping and suspension for the body of the paper cone in theconventional cone type of loud speaker,'whereby the moving partsincluding the cone may be rendered comparatively dead beat, particularlyat low frequencies.

Other objects may be found in the following detail description of apreferred embodiment of the invention and may be pointed out in theclaims.

Specifically, one object of my invention is to provide a damping for theedge of a sound radiator composed of material in an extremely expandedstate, extremely flexible, having high internal friction when bent andextremely small elasticity. Extremely soft felt is a good example ofsuch material. Ordinary felt or flannel or sponge rubber on the otherhand have too high a ratio of mass and elasticity to internal frictionto be valuably effective.

Referring to the accompanying drawing:-

The figure is a diagrammatic vertical crosssection of one embodiment ofmy invention, showing a cone type loud speaker having my improved loudspeaker cone suspension.

The numeral 1 indicates a conventional dydriver provided with aconventional movable voice coil 3 conventionally mounted at the apex 5of a paper cone 7 and suspended by a conventional centering spider. Aconventional frame 9 is mounted on member 1 and ter- 13 at its left endwhere it supports the outer edge 15 of my improved suspension 17 whichin this instance consists ofa strip of soft felt bent in the form of acircle.

Member 1'7 is clamped between member 13 and a conventional washer 19 bymeans of rivets 21--21 passing through the several members 13, 15 and19. Spacers 23-23 fix the amount of compression applied to member 15between membars 13 and 19 and thus facilitate uniformity of manufacture.

Member 1'? tapers toward its inner edge 25 which is sewed and cementedsecurely to the base of the cone 7. The taper of the member 17 ispreferably so proportioned that its inner flexible and light aspracticable, so as to avoid intenfering with high frequency vibrationsof the cone '7.

By high frequency I mean those frequencies at or above, for instance,512 cycles per second. By

low frequency I mean those frequencies below 512 cycles per second.

The body portion 27' of member 17 may be designed so as to bring intoaction the internal friction quality of the felt to the best advantageso as to damp the motion of the cone '7 and the voice coil 3 at lowfrequencies.

Among important factors in the design of member 17, it may be noted thatwhen the cone is in the indicated neutral position the fibres of the,felt in the body portion designed for radial flexure 2'7 should be freefrom tension. Thus the effect of the improved suspension will be toimpose damping friction between the fibres of the felt to control thelow frequencies.

In most of the current loud speakers of conventional type a thin softleather member under tension is used in place of my member 17. Suchleather raises the natural period of the cone and voice coil assemblyand thus places the fundamental resonant peak higher in the musicalscale which makes it more tolerable. With my improved suspension I seekto smooth out the peak.

While I have described my. improved suspension as being made of felt,other materials having similar physical properties may also be used.

Other positions on a paper cone than that described above may also bechosen for my felt member.

My improved felt or equivalent may be added to any ready to play loudspeaker radiator to damp its response at peak frequencies in accordancewith the progress of the art.

I claim:-

1. A suspension for the large end of a cone sound radiator including astationary frame, a ring of thick, soft, substantially untensionedmaterial supported at its outer edge in the frame, extending inwardly,decreasing in stiffness toward and. connected to the edge at the cone.

2. A loud speaker including a frame, a cone sound radiator, a driver inthe frame and attached to the apex of the cone, and a yielding supportfor the base of the cone consisting of thick, soft material having ahigh degree of internal friction, mounted on the frame, extendingunsupported and decreasing in stiffness toward the cone and attachedthereto at the more flexible edge.

3. A loud speaker including a frame, a direct acting sound radiatorprovided with a substantially continuous fibrous damping means at theedge thereof; said damping means extending unsupported from the frametoward the center 110,

of the radiator and being capable of radial flexure whereby damping maybe effected.

4. A loud speaker including a frame, a direct acting sound radiatorprovided with a substantially continuous damping means of materialinherently diffused and porous in both its natural and finished statesat the edge thereof; said edge being continuous, said damping meansextending toward the center of the radiator, and being capable of radialfiexure whereby damping may be effected.

5. A vibratory loud speaker radiator of direct acting size including anouter edge said edge being continuous, and front and rear surfaces, amember of extremely soft damping material, in an expanded and porousstate, at a surface, near the edge, coupled to the radiator andsubstantially free from initial tension to avoid radial compression ofthe edge thereof and a stationary frame substantially surrounding theradiator and member.

6. A vibratory loud speaker radiator of direct,

acting size including an outer edge, said edge being continuous, andfront and rear surfaces, a member of extremely soft fibrous, dampingmaterial, in an expanded and porous state at a surface, near the edge,coupled to the radiator to avoid radial compression of the edge thereofand a stationary framje substantially surrounding the radiator andmember.

7. A vibratory loud speaker radiator of direct acting size including anouter edge said edge being continuous, and front and rear surfaces, amember of extremely soft damping material, in an expanded and porousstate, tapered in stiffness toward the centre of the radiator andsubstantially free from initial tension, coupled to the radiator and astationary frame substantially surrounding the radiator and member.

8. A loud speaker including a frame and a direct acting sound radiatorprovided with a substantially continuous fibrous damping means at theedge thereof; said damping means extending unsupported except by theradiator and frame, from the frame toward the center of the radiator andbeing capable of radial fiexure whereby damping may be effected.

9. A loud speaker including a frame and a direct acting sound radiatorprovided with a substantially continuous fibrous damping means in anextremely diffused state and. containing a large percentage of voids, atthe edge thereof; said damping means extending unsupported except by theradiator and frame, from the frame toward the center of the radiator andbeing capable of radial fiexure whereby damping may 10. A loud speakerincluding a frame and a direct acting sound radiator provided with asubstantially endless fibrous damping means at the edge thereof; saiddamping means extending unsupported from the frame toward the center ofthe radiator and being arranged to flex in accordance with m vementthereof. said flexing being predominantly radial asaxial movement 01'the, radiator takes place.

11,. A loud speaker including a frame and a direct acting sound radiatorprovided with a substantially continuous fibrous damping means in anextremely diffused state and containing a large percentage of voids, atthe edge thereof; said damping means extending unsupported and in freeair from the frame toward the center of the radiator and being capableof radial flexure whereby damping maybe effected.

12. A loud speaker including a frame and a direct acting substantiallyconical sound radiator provided with driving means at the centre and anedge damping means of sufficient continuity to damp substantially theentire edge; saiddamping means consisting of thick loose textured porousmaterial tapering in thickness and designed for radial flexure.

CHARLES MESSICK.

